1. Field of the Invention
The present invention relates to an electron beam apparatus in use of an electron-emitting device applied to a flat type image forming apparatus a
2. Related Background Art
Conventionally, as a utilization mode of an electron-emitting device, an image forming apparatus is nominated. For example, there known is a flat type electron beam display panel with an electron source substrate (rear plate) having a great number of cold cathode electron-emitting devices being formed, an opposite substrate (face plate) comprising anode electrode and a fluorescent substance as a light emitting member being disposed in opposition in parallel and being exhausted to a vacuum state. A flat type electron beam display panel allows a plan to save weight and enlarge screen compared with a cathode beam tube (CRT) display apparatus that is currently being used widely. In addition, it can provide with images with higher luminance and with higher quality than those in another flat type display panel such as a flat type display panel in utilization of liquid crystal, a plasma display, an electro luminescent display etc.
Like this, in order to accelerate electrons emitted from a cold cathode electron-emitting device, it is advantageous for an image forming apparatus of such a type that applies a voltage between an anode electrode and a device to apply a high voltage in order to derive light emitting luminescence to the maximum limit. Corresponding with types of devices, emitted electron beams emanate before reaching the opposite electrode, and therefore, if a display with high resolution is intended to be realized, it is preferable that the inter-substrate distance between the rear plate and the face plate is short.
However, the inter-substrate distance gets shorter, then the electric field between the substrates gets high and therefore such a phenomenon that an electron-emitting device is destroyed by discharge becomes apt to take place. Japanese Patent Application Laid-Open No. 2003-157757 (U.S. Pat. No. 2003062843A) discloses a display apparatus having a resistant device being disposed on a connection route between a device electrode and wiring configuring an electron-emitting device in order to prevent influence due to discharge arising between an anode electrode and an electron-emitting device from reaching another electron-emitting device.
In the case where discharge arises between an anode electrode and an electron-emitting device, melting of an electrode and breaking taking place by the discharge might be accompanied by surface creeping discharge. That surface creeping discharge will be described with FIGS. 13A to 13F.
In FIGS. 13A to 13F, reference numeral 130 denotes wiring, reference numerals 131 and 132 denote device electrodes and reference numeral 139 denotes an insulating layer. Here, the upper surface is provided with an anode electrode (not shown in the drawing) and high voltage is applied.
The wiring 130 is formed by metal material with thicker film thickness and lower resistance than those of the device electrodes 131 and 132 and is connected to GND (ground). In addition, the device electrode 131 passes under the insulating layer 139 to extend to reach the wiring 130 and be electrically connected to the wiring 130. In addition, the device electrode 132 is connected to another wiring not shown in the drawing and is stipulated at a potential higher than that of the wiring 130.
In the configuration of FIGS. 13A to 13F, at first, discharge 133 arises in the device electrode 131 (FIG. 13A). Then, accompanied by progress in discharge, a cathode spot 134 arises (FIG. 13B). The cathode spot 134 refers to an electron-emitting point arising at the time of discharge and is an injection point of discharge current from the anode electrode (Reference: J. Appl. Phys., vol. 51, No. 3, 1414 (1980)). Since the cathode spot 134 moves to the negative potential side, the cathode-spot 134 goes for the wiring 130 close to GND here. As the discharge current increases, the device electrode 131 is heated and a melting portion 136 is generated (FIG. 13C). Therefore, resistance between the cathode spot 134 and the wiring 130 increases rapidly and consequently the potential of the device electrode 131 increases. That is, potential difference arises between the device electrodes 131 and 132 and surface creeping discharge 138 (discharge due to explosive increase in electron emission by an electric field) arises (FIG. 13D). Here, the route of the cathode spot 134 and the melting portion 136 remain as damage 137 subject to surface creeping discharge.
In addition, as a case different from FIG. 13C, the cathode spot 134 reaches at the end of the insulating layer 139 to stay at an end of the insulating layer 139 (FIG. 13E, the cathode spot 134 arises only in a portion that is exposed from the anode electrode). And, there is also a case (FIG. 13F) where the device electrode 131 is brought into melting and breaking so that surface creeping discharge 138 is caused to arise.
An actual electron beam apparatus has an electron-emitting device and an electric field enhancement coefficient of an electron-emitting device is high, and therefore surface creeping discharge to an adjacent electron-emitting device is apt to arise, requiring that potential increase is restrained to a low level.
The configuration disclosed in Japanese Patent Application Laid-Open No. 2003-157757 only controls the direction of flow of discharge current and will not prevent surface creeping discharge itself.